This invention pertains to a method and apparatus for providing a stable output voltage, and more particularly to a method and apparatus for providing large source and sink currents while maintaining a stable output voltage with significantly reduced noise and ripple.
Voltage regulators are well known in the art. These devices attempt to provide a stable, nearly constant voltage to a load. Further, these devices attempt to maintain the output voltage at the nearly constant value regardless of the current demands of the load.
Some regulators attempt to provide a stable output voltage by switching between an on state and off state, such as a switchmode solution. In such regulators, a voltage supply is switched off or short-circuited to prevent the load from receiving power from the supply, thus lowering the output voltage across the load. When the output voltage has reached a desired level, the supply is reactivated or the short is removed to allow the load to again be powered by the supply. This method provides slow response time and generally requires an excessive variation in the output voltage. Further, the switchmode techniques introduce unwanted noise into the system and output. Switchmode solutions provide voltage regulation, but generally are more costly to implement, generate excess noisy, have complicated designs and lack reliability.
In accordance with the teachings of this invention a novel method and structure is taught which provides for the regulation of an output voltage to stabilize the output voltage without limiting the output current. In one embodiment, the regulator includes a stabilizing circuit coupled to a source circuit and a sink circuit. The source circuit is configured to source an output current to the output, and the sink circuit is configured to sink the output current from the output. The stabilizing circuit is configured to transition the source circuit and the sink circuit between a conductive and nonconductive state to stabilize the output based on the voltage difference between the output and a reference voltage.
In one embodiment, the source and sink circuits each include at least one N-channel MOSFET transistor to source and sink output current. The stabilizing circuit includes a first and second amplifier, where the first amplifier couples with the sink circuit to transition the sink circuit between the conductive and nonconductive states, and the second amplifier couples with the source circuit to transition the source circuit between the conductive and nonconductive states.